1. Field of the Invention
This invention relates to a mechanism for converting alternating rotary motion to reciprocating motion, and more specifically to a mechanism comprising a yieldable transmission member engaged with the periphery of a pulley.
2. Background Art
Mechanisms for transforming rotary motion to linear motion are known in the art. One such mechanism comprises a flexible band engaged by a pulley wherein the pulley is rotated by a motor. The flexible band has an elongated slot throughout the length of one end of the band. The other end of the band is designed such that it can be inserted through the elongated slot as the mid portion of the band is wrapped around the pulley. A flexible band of this type is commonly referred to as a split band. The two ends of the band extend out from the pulley in opposite directions and are attached to opposite ends of an elongated member. As the pulley rotates, one end of the band is wrapped up by the pulley while the other end unwraps effectuating a corresponding translational motion to the elongated member.
This type of mechanism is useful in a disk drive system for imparting linear movement to a magnetic head carriage that is mounted on a member that is driven by the motion of the flexible band. A magnetic head carriage typically comprises a stationary lower recording arm and a pivotally mounted upper recording head. Thus, the position of a recording head may be changed linearly along the radius of a disk to access a desired track.
Flexible, or floppy disk drives are well known in the data processing industry, and are presently widely utilized as a primary peripheral input/output device for personal or home computers. These disk drives typically use a flexible five and one-fourth inch disk contained within a flexible cartridge or envelope. Such drives are typically of the well-known "full height" or "half-height" variety. With the advent of the high use of these computers in home and business, these disk drives have a correspondingly high usage rate.
These disk drives that have utilized head carriage and head access mechanisms for transforming rotary motion to linear motion, as described above, have had problems associated with them. One such problem is that the mechanisms were assembled either inside, or outside the disk drive assembly using a variety of small, hard to manipulate parts. As a result, it was difficult, time consuming, and costly to assemble the disk drives. In addition, those mechanisms that were assembled outside of the drive assembly were attached to rigid massive yokes that made damage to the band likely if this structure were handled improperly during assembly.
Poor reliability and inaccurate operation is another problem with the previously stated mechanism where the ends of the flexible band were connected to a rigid massive yoke. Since the pulley and motor are typically mounted to the disk drive frame, and the yoke is attached to the head carriage assembly, inherent manufacturing tolerances may cause the yoke to be too close or too far away from the pulley. If the yoke is not accurately positioned relative to the pulley, i.e. the yoke is too close or too far from the pulley, the ends of the band will assume a V-shape as they leave engagement with the pulley, and the output motion will be arcuate, not linear. As a result, after the head carriage assembly is attached to the yoke, and during actual operation, this arcuate motion could produce improper head movement relative to the disk, causing inaccurate operation and poor reliability.
Another problem which has heretofore been recognized, and which affects the reliability and accuracy of head access mechanisms, involves vibrations of this mechanism which can cause head transducing errors. It has been necessary to damp these unwanted vibrations for reliable and accurate operation of the mechanism. However, damping mechanisms that have previously been used have made the assembly of disk drives even more difficult, time consuming and costly by the associated added hardware.
In this document, the term carriage, head carriage, or head carriage assembly will be used to mean a structure which comprises a stationary lower recording arm and a pivotally mounted upper recording head. The term head access mechanism shall be used to mean an assembly of parts comprising a motor, pulley, band, and tensioner which work together to transform the motor's rotary motion to linear motion of the tensioner.